In wireless network environments such as cellular networks, network entities are provided to facilitate the communication between communicating devices on the network. In Global System for Mobile communications (GSM) networks, Base Station Systems (BSS) are provided on the network, which include one or more Base Transceiver Stations (BTS) and a Base Station Controller (BSC). The BTS manages the radio interface to Mobile Stations (MS) and/or other terminals, and includes the transceivers and antennas to service each cell. A group of BTSs are controlled by a BSC, which provides the control functions and physical links between the Mobile Switching Center (MSC) and the BTS. The BSC performs high-capacity switching functions, including handover and control of radio frequency (RF) power levels in BTSs.
If there is no active connection between a terminal and a BSS, the terminal is at rest or in “idle” mode, and the BSS has no specific tasks to perform relative to the terminal. However, the terminal continues to monitor control channels such as the Broadcast Control Channel (BCCH) or the Packet Broadcast Control Channel (PBCCH) of the current and neighboring cells, to facilitate location update operations.
During a connection, i.e. when the terminal is in transfer mode, power control functions serve to maintain and optimize the radio channel. It is very important that terminals that send data to the network use the proper output power level. If the output power level of the terminal is too low, data throughput may suffer due to errors caused by sub-optimal radio conditions. If the output power level of the terminal is too high, excessive power consumption results, and the data transmission may cause interference to other channels used by other terminals.
In General Packet Radio Service (GPRS) data transmissions, the terminal determines the appropriate output power levels using specified formulas. These formulas include parameters that the terminal obtains from various sources, namely from system information messages broadcast by the network, or from control messages that are sent specifically to each of the terminals. Such system information messages are transmitted by the network in two possible logical channel structures, depending on the base selected by the network operator. If packet channel structure exists, the system information messages are transmitted on the PBCCH; otherwise the system information messages are transmitted on the BCCH.
As described above, the terminal may operate in different modes, such as idle and transfer modes. The terminal is able to use different frequency bands in these different modes. For example, when in idle mode, the terminal may listen for system information messages in the 900 MHz band. The terminal may therefore receive terminal output power level indications via system information messages from the BCCH channel in, for example, the 900 MHz band. When in transfer mode, the network may allocate the traffic channel in a different band, such as the 1800 MHz band. However, the terminal output power level indications provided via this different frequency band (e.g., 1800 MHz band) may be different or unavailable than that provided via the control channel in the other band (e.g., 900 MHz band). This may be problematic, as the terminal has received conflicting parameters or other information for use in determining the proper terminal output power level to be used by the terminal. Thus, in current practice, the terminal has difficulties in determining the correct output power level to be used when the Traffic Channel (TCH) is mapped on a different band than the common channels such as BCCH/PBCCH, and vice-versa. Due to this discrepancy, poor connection quality, errors in transmission, interference or other undesirable radio connection characteristics may result.
Further, the terminal output power level to be used by the terminal may depend on the particular cell/BSS in which the terminal is operating. Therefore, when handover occurs, the output power of the terminal may not be set correctly. Further, new modes such as the Dual Transfer Mode (DTM) allows the terminal to operate simultaneously in packet-switched (PS) and circuit-switched (CS) modes. When operating in these different modes, and when handover occurs, the output power of the terminal may not be set correctly. This problem cannot reasonably be solved using the system information messages, since it requires a significant amount of space in already heavily loaded messages. Furthermore, defining the parameter for various different frequency bands in the system information messages is not flexible, as new frequency bands may be defined in the future.
Accordingly, there is a need in the communications industry for a manner of properly establishing the terminal output power levels in changing circumstances. These changing circumstances include, but are not limited to, situations where the common broadcast channel is mapped on a different band than traffic channels, handover, DTM implementations and the like. A further need exists for a system and methodology that provides an unintrusive and efficient manner for providing such information, while working within existing protocols and structures. The present invention fulfills these and other needs, and offers other advantages over the prior art.